[TUHS] Why do compress(1) and pack(1) use the .Z / .z extension?

[Clem Cole]

I thought the gz was because dos voilf not tell the difference between Z
and z which was strange of course since it stored it on 8 bits unlike rt11
which used RAD50 (5bits)  sigh.

On Fri, Nov 27, 2020 at 2:00 PM Warner Losh <imp at bsdimp.com> wrote:

>
>
> On Fri, Nov 27, 2020 at 10:17 AM Clem Cole <clemc at ccc.com> wrote:
>
>>
>>
>> On Fri, Nov 27, 2020 at 8:08 AM Hans Wennborg <hans at hanshq.net> wrote:
>>
>>> I'm trying to find out why compress(1) uses .Z as filename extension.
>>>
>>> My theory is that it was inspired by pack(1), which uses the .z
>>> extension.
>>>
>> Yes.
>>
>>
>>
>>>
>>> However, I haven't been able to find any info on why pack(1) uses that
>>> extension. Does anyone here know?
>>>
>> No idea - but yes, Zucker used a .z at Rand when he wrote.
>>
>>>
>>> Some searching led me to [1] which is a man page for pack from AUSAM.
>>> It's written by Steve Zucker in 1975, so perhaps the extension is z for
>>> Zucker?
>>>
>>> Was Zucker's pack(1) the first, though? This message [2] talks about a
>>> Bell version.
>>
>> Zucker wrote it at Rand - early/mid 1970s. IIRC, It was later included in
>> the original Harvard USENIX tape in the 'Rand' directory.  I believe that
>> Rand Pipes (named pipes) are in the same directory. Although some of the
>> Rand stuff was being shared by folks on the ArpaNet before USENIX existed
>> and I think it made it to the wild before the first USENIX tape.
>>
>> It was really important back in the day.  Remember RK05's are only 2.5M
>> bytes - source archiving and packing files was pretty important given the
>> cost / byte of disk.
>>
>> I think there may have been an early version @ BTL - PWB may have
>> distributed it also, but I'm fairly sure it was the Rand code that started
>> it.  Noel might remember more than I.  I'm 90% sure we had it at CMU before
>> we got either PWB 1.0 or UNIX/TS from Ted -- I want to say it we had it on
>> 5th edition but maybe not.
>>
>> One of the PDP-10 folks will need to chime in here.  My memory is there
>> was something like pack(1) on the CMU PDP-10s and 20s that I saw before I
>> saw the UNIX tool [not sure why I think this, but it may have been SAIL
>> program - I remember looking at a number of simple tools when I learn SAIL
>> years and years ago - 74/75-ish].  IIRC they were not exactly the same
>> format as the 10's were 36-bit words, stored 5 chars in a word, but it was
>> the same idea.
>>
>
> Regardless of the early history, this is why gzip files end in .gz and not
> .z. The pack'd files were considered too prevalent at the time to crowd
> into that name space, even though this happened maybe 12 years after
> compress started to displace pack.
>
> Warner
>
-- 
Sent from a handheld expect more typos than usual
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